The present disclosure relates to a hybrid type fiber filtering apparatus, and, more particularly, to a hybrid type fiber filtering apparatus which is formed in a duplex type in order to reduce the space it occupies. Raw water may be filtered by an upper-layer fiber filter and a lower-layer fiber ball filter so as to enhance filtering performance.
In general, filtering apparatuses supply clean, treated water by filtering polluted raw water through a filter, and have been used not only for drinking water but also for waterworks, sewage treatment, and factory water treatment. These filtering apparatuses have been used for river water treatment, factory waste water treatment, and in seawater desalination. They are a growing trend which increase the treatment quantity and improve water quality.
There are various multitype filtering apparatuses which are used for large-capacity water treatment such as a multitype pore control fiber filtering apparatus. Moreover, in order to enhance treatment speed and water quality, there are apparatuses which use a plurality of filters in which multiple filtering stages are arranged in one filter tank. For example, a pore controllable two-step net fit fiber filtering apparatus may be used. Furthermore, in some cases, a method for re-filtering water produced by filtering through an additionally-mounted cartridge filter may be used in purification plants, water treatment plants, and seawater desalination plants. However, such a method requires multiple installation sites and increased expenses. In summary, such a method has a disadvantage in that the filtering apparatus needs an installation site that is very wide and is very expensive due to the increased occupation space or installation space.
Filtering materials used in filter apparatuses are typically sand or anthracite, but such filtering materials have several issues in that floating materials in a trapped space are limited to its surface layer, and, by consequence, blockage occurs easily and is difficult to clean. Therefore, a dual media filter and a pore control fiber filter may be used in an attempt to solve the above-mentioned problems.
However, the dual media filter has a disadvantage in that it is difficult to provide filtering through multiple layers because most of the filter media agglomerates together.
In a fiber filter that is used in a pore control fiber filtering apparatus, fiber yarns having minute filaments are tied into bundles, and then the fiber yarn bundles are arranged in the water's path to serve as filtering materials. The fiber filter has advantages in that it provides excellent filtering performance because pores formed by the filaments are easily controlled by a physical control. It also has a long lifespan because it is easy to clean. Particularly, the fiber filter performs better than other filtering methods because of its removal efficiency of particles and algae existing in water as suspended solids.
However, most of the pore control fiber filters adopt a strainer method in that a strainer is arranged in the middle of an enclosure and the fiber filter is arranged outside the strainer. In the strainer raw water passes through the fiber filter. In this case, because the width of the fiber filter is thin, the subsequent filtering path is short. A method of forming the fiber filter in multi-layer may be used in an attempt to solve such a problem, but this method has problems in that efficiency is deteriorated and manufacturing costs are increased due to flocculation of the fiber filters or due to complexity in structure.
On the other hand, in order to control pores of the fiber filter, a method using hydraulic pressure of raw water has been used. Recently, a method for twisting and winding the fiber filter around a perforated pipe of the strainer or pulling the fiber filter up and down so as to compress or loosen the fiber filter has been used, for example in a pore controllable filtering apparatus.
Such fiber filtering apparatus provide a good filtering effect in an early period of use because the tensile force or a torsional tension is evenly transferred to each fiber so as to tighten upper, middle and lower portions of the subsequent filtering layer. However, when the fiber filtering apparatus is used repeatedly, the filtering layer is not formed properly and filtering performance is deteriorated because the length of the fiber is enlarged and the tensile force or the torsional tension is not evenly applied to each part of the fiber.
Additionally, in a case where raw water containing suspended solids or sludge of high concentration is treated, sediments of the raw water are concentrated or precipitated in a lower part of a filter tank, which impedes backwash to the lower portion of the fiber filter.
In addition, when the fiber filter is backwashed repeatedly, the fiber filter is stretched, and hence, the fiber filter cannot easily control pores because foreign matter stained on the fiber filter is not removed even though backwash is carried out.
Therefore, it is desirable to improve the fiber filtering apparatus to reduce the occupation space but also have a sufficiently long filtering path to control pores smoothly, to compensate a change in tensile force of the fiber filter, and to effectively clean the lower part of the fiber filter.